1. Field of the Invention
The present invention relates to a specimen holder for holding a specimen in the electron beam path within a transmission electron microscope (TEM) and, more particularly, to a specimen holder which permits imaging of the specimen while supplying electrical current to the specimen or taking an electrical signal from it.
2. Description of Related Art
Since a TEM enables high spatial-resolution imaging and analysis, the TEM is an instrument indispensable for evaluation of materials in the submicroscopic domain. The TEM makes it possible to perform high spatial-resolution imaging. In addition, variations in the specimen can be observed while heating, cooling, or stretching the specimen or applying a voltage to the specimen. In this way, a richer amount of knowledge can be derived from the specimen. Consequently, TEMs are used in many material fields.
For example, in a specimen used in the semiconductor microelectronics field, the resistance value of the specimen is measured while electrically energizing the specimen or taking an electrical signal from the specimen before and after the energization. Thus, information about the characteristics of the material of the specimen can be obtained. However, since the specimen observed on the TEM is placed in the narrow gap between the objective lens polepieces, limitations are imposed on the shape and functions of the specimen holder. Techniques regarding specimen holders permitting such measurements and observations are disclosed in Japanese Patent Laid-Open No. 2003-35682 and Japanese Utility-Model Laid-Open No. H5-69660.
Japanese Patent Laid-Open No. 2003-35682 discloses a technique for measuring the electrical characteristics of the inside of an LSI having a design rule of about 0.1 μm using a focused ion beam (FIB) machine and a TEM. In this technique, a pair of very thin conductors is moved into a desired measurement site on the specimen by a manipulateór. The conductors are fixed to the measurement site by FIB processing. Then, the specimen holder is removed from the FIB machine and attached to the TEM or other apparatus. Then, measurements and observations can be carried out. In this method, however, a probe for measurement must be fixed to a desired measurement site by the manipulator and FIB machine before the specimen is placed on the TEM. Therefore, even if a desired measurement site is found from the results of high-magnification TEM image observation, the site cannot be measured.
Japanese Utility-Model Laid-Open No. H5-69660 discloses a specimen holder used for measurement of electrical resistance. This holder is employed in a four-terminal method in electron microscopy. The holder has two opposite specimen supports across which a specimen is placed. A lead wire for applying a voltage to the specimen is previously connected with the opposite specimen supports. Two terminals for measuring the voltage drop across the specimen are connected with the specimen via the two specimen supports. In this method involving bringing the two terminals into contact with the specimen, however, a quite thin lead wire is directly soldered to ends of the specimen or electrical conductivity is obtained by wire having resilience. Consequently, it is impossible to make measurement at a microscopic measurement site selected on the specimen.